1. Field of the Invention
The present invention relates to a fluorinated oligomer having COOH groups at both end, a process for producing the same and a composition comprising the same together with epoxy resin, and more particularly to a fluorinated oligomer having COOH groups at both ends, obtained by decomposition of fluorine rubber crosslinking products, a process for producing the same and a composition comprising the same with epoxy resin.
2. Description of Related Art
Utilization of ordinary rubber wastes by regeneration has no positive cost merits, but utilization of vulcanized fluorine rubber wastes, typical of which are flashes generated during the rubber vulcanization-molding, is an important task from the viewpoint of cost reduction, because the high raw material cost of fluorine rubber.
So far, the cross-linked, vulcanized fluorine rubber has been regenerated by mechanically pulverizing flashes, waste pieces, etc. of the crosslinked, vulcanized fluorine rubber, followed by plasticing, or by further treatment with nitric acid, potassium permanganate or various amines [JP-A 59-217734 and 59-217735; U.S. Pat. No. 3,291,761; DP-A 2 360 927 and 2 420 993; Kautschuk+Gummel.multidot.Kunststoffe 23. Jahrgang, Heft March 1976, page 218 and ibid. 45. Jahrgang, Nr. September 1992, page 742; Proiz-vo Shin, Rezinotekhn; Asbestotekhn. Izdfii (Moskva) 1979,vol. 6, page 7]. The regenerated fluorine rubber is mixed with virgin rubber (fresh rubber) as a filler and is used as a kind of extender.
However, the crosslinking structure of the crosslinked, vulcanized fluorine rubber must be decomposed to obtain the regenerated fluorine rubber from the crosslinked, vulcanized fluorine rubber. Furthermore, the vinylidene fluoride structure of vinylidene fluoride copolymer usually used in the fluorine rubber is actually hard to decompose under basic conditions or the crosslinking structure based on polyhydroxy compound (polyol) is not so decomposed even with a strong acid such as nitric acid, etc. as to regenerate and isolate the rubber moiety.
Still furthermore, the crosslinked, vulcanized fluorine rubber contains a filler in almost all the cases, and it is desirable to obtain regenerated fluorine rubber completely freed from such a filler. It is pointed out that the above-mentioned regeneration procedure is not always applicable, depending on the crosslinking system used for the formation of crosslinked, vulcanized fluorine rubber, and thus is not generally applicable.
On the other hand, U.S. Pat. No. 3,291,761 discloses a process for reclaiming revulcanizable polymers by dehydrogenfluoride reaction an amine-vulcanized vinylidene fluoride-hexafluoropropene copolymer and subjecting the resulting double bonds to oxidative decomposition, using KMnO.sub.4. Antipollution countermeasures are indispensable to the process with respect to removal of heavy metal Mn.